We request funds to purchase a Nikon A1R Confocal Microscope system to replace our 10 year-old Zeiss/BioRad Radiance system that Zeiss can no longer guarantee to support or repair. The new instrument will be housed within the Program in Membrane Biology (PMB) Microscopy Core at the Massachusetts General Hospital (MGH) in the multidisciplinary Simches Research Center building. The mandate of this MGH- approved Core facility is to provide access to a full range of techniques using microscopy and imaging to individual research groups, 3 NIH funded Centers and 3 Thematic Centers within the MGH community and beyond. Over the past few years, the Core has developed considerable expertise in static and live cell imaging techniques but has fallen behind in providing sophisticated fluorescence methodologies due to the age of our existing equipment and its lack of appropriate laser lines and other hardware options. The three major reasons for this application are: 1) To ensure that we can continue to provide routine confocal microscopy services to our extensive Core user base in the face of an old and potentially non-repairable existing system;2) To expand our Core capabilities to provide state-of-the-art fluorescence modalities including FRET, FRAP and molecular uncaging techniques to our user base;3) To improve our multiwavelength live cell imaging capabilities that are at the moment limited by the absence of appropriate laser lines and poor dual-color sensitivity on our existing 2003 vintage Perkin Elmer spinning disk live cell imaging system. Since the PMB Core was founded in 1986, it has become a central part of the MGH/HMS medical research community. Over 30 NIH-funded PIs and their numerous lab members within the HMS/MGH and in other institutions made significant user of the Core confocal in the past 12 months alone, and we have supported literally hundreds of peer-reviewed publications from our user base over the years. The Core has an ongoing quest to constantly improve and upgrade Core facilities in support of its user base. This has been achieved using funds from NIH SIG applications as well as considerable institutional support from the MGH leadership. Providing our Core user base with continued access to an up-to-date fluorescence imaging platform is essential to maintaining the MGH community at the cutting edge of NIH-funded, health-related research.